This invention relates to a scroll compressor utilizing an abradable coating over a portion of its wrap only such that the abradable coating will provide a tight tip seal, but the uncoated portions of the wrap will provide a load-bearing surface.
Scroll compressors are becoming widely utilized in refrigerant compression applications. In a scroll compressor, first and second scroll members each include a base and a generally spiral wrap extending from the base. The wraps interfit to define compression chambers. One of the two wraps is caused to orbit relative to the other, and as the two orbit, the compression chambers are decreased in volume, thereby compressing an entrapped refrigerant.
In scroll compressors, the tip of each wrap is ideally in contact with the base of the opposed scroll member. A prior art scroll compressor is shown in FIG. 1. In prior art scroll compressor 20, the orbiting scroll 22 is placed into operable relationship with the non-orbiting scroll 24. The orbiting scroll 22 has a wrap 26 extending from its base 27. The wrap 26 contacts the opposed base 29 of the non-orbiting scroll 24. The wrap 28 from the non-orbiting scroll 24 contacts the base 27. Ideally, the tips of the wraps are in abutting contact with the opposed bases.
However, as shown in FIG. 2, it is often the case that local height variation along the wrap length may prevent sealing contact with the floor of the opposed base. The leakage sensitivity to a given gap is greater near the center of the wrap in that pressure will be higher adjacent the center. This leakage over the tip of the scroll compressor and through the gap 23 is undesirable and reduces efficiency.
Scroll compressors have been proposed wherein a coating has been applied along the entire wrap. However, this has undesirable characteristics.